Many turtles and lizards, and all crocodilians, are known to have temperature-dependent sex determination (TSD)(Bull, 1980). Instead of an individual's sex being determined by specific sex chromosomes, sex is determined in species with TSD by the temperature at which the egg is incubated. Because of TSD, it becomes important to determine the impact of present management practices on the conservation of endangered turtle species. Evidence to date indicates that previous efforts may have produced mainly males, thereby hindering conservation and recovery efforts. In addition, the incubation of turtle eggs at temperatures that will consistently produce females usually results in significant thermally-induced mortality. The method of the present invention represents an alternative for producing female individuals without thermal mortality. Further, these estrogen-treated individuals are fertile as adults. When applied to endangered reptiles species, this technique would significantly improve the recovery of wild populations by skewing the population sex ratio to one that favors reproductive females.